Localized magnetic field depressions in the inner magnetosphere, known as magnetic dips, are produced by the diamagnetic motion of energetic ions injected via substorm activities. The magnetic dips, if deep enough, can produce a local minimum in the radial profile of the field strength to trap the injected protons. Therefore, the trapped protons would drift at the same speed as the dip propagation, which leads to the simultaneous enhancements of proton fluxes in multiple energy channels at the leading edge of the dip structure. On the trailing side, the reduction of proton fluxes shows dispersive features, which can be attributed to the energy-dependent drift motion of the injected protons in the absence of the local field minimum. This scenario is examined based on comparisons between multi-spacecraft observations and test-particle simulations, and their good agreement validates the scenario to shed new light on the dynamics of the inner magnetosphere-magnetotail coupled system.

magnetic dip,diamagnetic motion,inner magnetosphere,energetic protons,ring current,substorm injection